I would go further and say that plain text (yes, I know org-mode is plain text too) would work just as well. Each board is a directory. Each column in a board

I would go further and say that plain text (yes, I know org-mode is plain text too) would work just as well. Each board is a directory. Each column in a board is a file. Each task is a line in the file. Open up the directory in the text editor of your choice. Move tasks with your normal cut & paste commands that you use for everything else. Keep the whole thing in version control.